Devices referred to as microanalysis chips or μTAS (Micro Total Analysis Systems) have been put to practical use, in which using a microfabrication technology, micro-channels and circuits are formed on a silicon or glass substrate, and thereby chemical reaction, separation, or analysis is carried out in a micro-space by introducing a liquid sample such as a nucleic acid, protein, or blood into such micro-channels. It is conceivable that these micro-channel chips have such advantages that the used amount of a sample or a reagent or the discharge amount of waste liquid is reduced, and small-foot print, portable, and inexpensive systems are realized.
Micro-channel chips are manufactured in such a manner that 2 members in which at least one member thereof has been subjected to microfabrication are bonded together. Conventionally, for micro-channel chips, glass substrates have been used and various microfabrication methods have been proposed. However, such glass substrates are unsuitable for mass production and exhibit extremely high cost. Therefore, the development of resin micro-channel chips, which are inexpensive and disposable, has been desired.
As a method for manufacturing a resin micro-channel chip, a method for joining a resin substrate in which a channel groove is formed and a resin substrate to cover a channel groove is available. To join resin substrates together, listed are a welding method to join resin substrates by heating using a heating plate, hot air, a heating roll, ultrasound, vibration, or a laser, a joining method to join resin substrates using an adhesive or a solvent a joining method utilizing adhesion properties of resin substrates themselves; and a substrate joining method via surface treatment such as plasma treatment for resin substrates (for example, refer to Patent Document 1).
FIG. 10 is a schematic cross-sectional view in which a resin substrate has been formed by pouring a resin into a conventional micro-channel chip molding die. When a resin substrate is joined, as shown in FIG. 10, a melted resin is poured into a micro-channel chip molding die 100 (the portion expressed by oblique lines) and then cooled to mold a resin substrate 001 (the filled-in portion) having a channel groove. The micro-channel chip molding die 100 has a micro-structure 102 to carry out transfer to a surface 101 for transferring a channel groove to a resin substrate (hereinafter referred to as a “molding transfer surface 101”). Then, the micro-channel chip molding die 100 transfers a micro-structure 102 provided for its own molding transfer surface 101 to a poured resin to mold a micro-channel 002 as shown in FIG. 11. FIG. 11 is a schematic cross-sectional view showing the time of mold release molding (releasing a resin substrate from a die) after a resin has been poured into a conventional micro-channel chip molding die.
However, as described in Patent Document 1, in molding in which a micro-channel chip molding die 100 having a micro-structure on the molding transfer surface is used, due to the effect of molding shrinkage with cooling of a resin substrate 001 itself and the runner section being a section to pour a resin into a die, the resin in the edge portion of the micro-structure is raised or broken during releasing. Thereby, as shown in FIG. 11, there occurs a phenomenon in which deformation 003 is generated in part of a resin substrate 001 having been removed from a die 100 in the order of submicron—about 5 μm. In this molded resin substrate 001, for joining as described above, the joining surface (the portion where 2 resin substrates are bonded) in which a micro-channel 002 is formed is required to exhibit high flatness. Namely, when the flatness of the joining surface is degraded due to deformation occurrence as described above, it may be difficult to join resin substrates 001 or to form a micro-channel 002.